Experiments will be performed in two-kidney clip hypertension and spontaneous hypertension in rats using diuretics and agents which either promote or prevent intravascular coagulation to study the influence of sodium balance and coagulation on the transition between benign and malignant hypertension. Radiographic and microdissection techniques will be used to explore the role of tubular obstruction in post-ischemic acute renal failure in the rabbit. Experiments will be performmed to investigate the role of various hormones in the beneficial effect of guanethidine and fragmented renal medulla in post-ischemic acute renal failure.